1. Field of the Invention
The present invention relates to a solid-state image pick-up device, so-called honeycomb CCD, which is to be used in a digital still camera, having a high fineness and picture quality and more particularly to a suitable solid-state image pick-up device for a digital still camera having a focal plane shutter and the digital still camera.
2. Description of the Related Art
FIG. 11 is a plan view showing a conventional solid-state image pick-up device described in JP-A-10-136391, for example. The solid-state image pick-up device is referred to as a so-called honeycomb pixel arrangement, and photodiodes (photoelectric converting devices) having a large number of green (G) color filters are provided at a predetermined interval vertically and horizontally and photodiodes having blue (B) and red (R) color filters are alternately provided in positions shifted by a ½ pitch from each photodiode in each row and column.
In the shown example, octagonal frames described as “R”, “G” and “B” indicate red, green and blue color filters respectively, and corresponding photodiodes are provided on the lower side thereof (the lower side of the paper).
An electric charge stored in each photodiode is read onto a vertical transfer path 20 formed on the side of each photodiode as shown in an arrow of “a”, and is transferred along the vertical transfer path 20 as shown in an arrow of “b” to reach a horizontal transfer path 21, and is then transferred along the horizontal transfer path 21 as shown in an arrow of “c” and is thus read out of the solid-state image pick-up device.
An image processing device provided in the rear stage of the solid-state image pick-up device which is not shown from the amount of the G signal charges read from a G pixel provided around an “R” pixel in addition to the amount of R signal charges read from an “R” pixel position shown in FIG. 11, for example, and similarly estimates the amount of B signal charges in the R pixel position from the amount of the B signal charges read from a B pixel provided around the R pixel. More specifically, the amounts of signal charges having three colors of R, G and B in each pixel position are obtained and a pick-up image can be acquired with a resolution equal to the number of pixels.
As shown in FIG. 12(a), furthermore, the amount of signal charges in a place kin which a pixel is not provided is estimated by carrying out an interpolating operation over pixel signals of R, G and B therearound. By using an estimated charge amount on the k point (which will be hereinafter referred to as an imaginary pixel point), it is possible to generate image data on the imaginary pixel point, thereby obtaining an image having a higher resolution than the number of pixels of the solid-state image pick-up device as shown in FIG. 12(b).
As described above, conventionally, a signal charge on an imaginary pixel point k is estimated from surrounding pixel signals so that an image having a high resolution can be obtained. However, the amount of the signal charges on the imaginary pixel point k is persistently estimated from the surrounding pixel signals and the estimation value is different from an actual amount of the signal charges. For this reason, there is a problem in that the effect of enhancing a resolution cannot be obtained in all scenes even if the estimation value is used.
A false signal such as a moiré is generated in a solid-state image pick-up device. Turning back to JP-A-10-136391, it has proposed a solid-state image pick-up device capable of increasing an amount of a light to be received to enhance a light receiving efficiency while increasing the integration of a pixel. The solid-state image pick-up device provides a novel structure capable of optimizing the space sampling of an image. This structure is referred to as a so-called honeycomb pixel array.
In this honeycomb pixel array, if a distance between pixels is set to be a pitch, an arrangement is carried out with a shift of a half pitch in a row direction and/or a column direction, for example. With this pixel arrangement, a transfer register in a vertical direction is formed to meander so as to go around each pixel in a solid-state image pick-up device of a CCD (Charge Coupled Device) type. A color filter segment is assigned to each of pixels (actual pixels) present actually. In the pixel (photoreceptor), a light transmitted from the color filter segment is photoelectrically converted and a signal charge having a color attribute is read onto a vertical transfer register in a vertical direction. In the solid-state image pick-up device, a voltage signal obtained by a Q/V conversion, that is, an analog signal is output through a horizontal transfer register which is orthogonal to a vertical transfer direction.
The analog signal is subjected to a signal processing. In consideration of the color of the actual pixel which is supplied, the correlation of pixel data is acquired. In the signal processing, a color is set, and pixel data in a position in which a pixel is not actually present, that is, pixel data in a virtual pixel and pixel data in a pixel having a different color which is actually present are calculated by using pixel data having the same color and a high correlation. A pixel interpolation processing is carried out by using pixel data in such a direction as to have a high correlation. In the pixel interpolation processing, the generation of a false signal can be suppressed. Moreover, the broadband processing of the pixel data is also carried out to increase a resolving power.
In the signal processing, the correlation of pixel data present around an object pixel is decided to carry out a prediction, thereby generating an object virtual pixel. However, the signal processing does not produce a great advantage for all scenes. If the prediction is erroneously carried out, pixel data to be generated cannot reflect a faithful color and gradation, for example. As a result, there is a possibility that a false signal for an original scene might be generated and a resolution might be deteriorated.